Problem with CVS access to current sources

Dear PostgreSQL gurus,

first of all, many thanks to everyone involved in writing and
enhancing PostgreSQL! It has grown enourmously during the last
months and is a most impressive system.

Sorry if this has been dealt with, but in the last few days,
I have not been able to access to PostgreSQL anonymous cvs server.

The command

cvs -z3 -d :pserver:anoncvs(at)postgresql(dot)org:/usr/local/cvsroot co -P pgsql

returns

Fatal error, aborting.
: no such user

(it's called from a script and has worked flawlessly for quite a while
before; I have not noted any change in the description of CVS access
at the WWW site...). Repeating the cvs login did not change the result
of the checkout call...

I'd very much appreciate any hint on what error I might make ...

Best regards,

Ernst